import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> ans = new ArrayList<List<Integer>>();
        Arrays.sort(nums);
        for (int i = 0; i < nums.length-2; i++) {
            if (i == 0 || (i > 0 && nums[i] != nums[i-1])) {
                int low = i + 1, high = nums.length - 1;
                int sum = 0 - nums[i];
                while (low < high) {
                    if (nums[low] + nums[high] == sum) {
                        ans.add(Arrays.asList(nums[i], nums[low], nums[high]));
                        while (low < high && nums[low] == nums[low + 1])
                            low++;
                        while (low < high && nums[high] == nums[high - 1])
                            high--;
                        low++;
                        high--;
                    } else if (nums[low] + nums[high] < sum) {
                        low++;
                    } else {
                        high--;
                    }
                }
            }
        }
        return ans;
    }
    public static void main(String[] args) {
        int[] nums = {-1, 0, 1, 2, -1, -4};
        Solution s = new Solution();
        s.threeSum(nums);
    }
}